One or more deformations present within a sheet of a medium to be printed can cause serious reliability problems in a printing system, such as an inkjet printing system, where there is only a small gap between a sheet transport mechanism and an image forming device or printing head of the printing system. If the sheet to be printed touches the image forming device or the printing head as a result of such a deformation, this can lead to print quality degradation and/or to a sheet jam in the machine. To achieve high print quality in an inkjet printing system, the distance between the printing heads and sheet to be printed should be kept small. Because of this small distance (print gap) the print heads are easily touched by the sheets as they pass. Accordingly, even small defects like dog ears, wrinkles, tears etc. can cause a so-called “head touch”, which can degrade print quality, cause nozzle failure, or even sheet jams.
To address these issues, systems have been developed which employ a proofing device capable of identifying sheet deformations and rejecting sheets that contain such deformations. However, there are many sources of defects or errors that may degrade the productivity of a printing system. For example, sheets to be printed supplied to a printing machine may already contain various defects. Also, defects and wear within the machine can cause the sheets to become damaged. Changes in the environmental conditions can lead to deformation of the sheets as they are being processed, and inappropriate settings in a printing system, such as too much ink or a drying temperature that is too high, can also generate problems. Furthermore, such influences or defects can act in combination, so making it very difficult to identify a root cause of a problem.
US2004100016 A describes a media qualification device wherein sheets may be sorted among a plurality of usable media paths according to media grade. The media qualification device may further comprise an input/output device configured to select media grade parameters.